Dec 20, 2023 04:50 AM
'Mass delusion and wishful thinking': Why everything you think you know about methane is probably wrong
https://thebulletin.org/2023/12/mass-del...bly-wrong/
INTRO (excerpt): . . . The popular narrative suggests that tackling methane emissions is the “low-hanging fruit” in the climate-solutions toolbox. The belief that turning off the taps on this “super-pollutant” could “buy us time” to address the climate crisis is widespread, shared by politicians, journalists, and even some scientists.
But this is a dangerous fallacy, according to Raymond Pierrehumbert, a professor of physics at the University of Oxford and a member of the Bulletin of the Atomic Scientists Science and Security Board.
In an in-depth interview with Bulletin climate editor Jessica McKenzie, Pierrehumbert dissects the Oil and Gas Decarbonization Charter—the voluntary pledge made at COP28 by some oil and gas companies to slash operational emissions of greenhouse gases, including bringing methane emissions to “near-zero.”
He goes on to explain why describing methane as “80 times as potent as carbon dioxide” is inaccurate and misleading, and why the widespread hope that sharp cuts to methane emissions will bring about immediate and significant reductions of global temperatures is both wrong and distressing.
- - - INTERVIEW EXCERPT - - -
Raymond Pierrehumbert: . . . Now as far as methane goes—that’s where we get into the subtler issue of just what is carbon dioxide equivalent, or just all the fallacies associated with the term carbon dioxide equivalent, because the standard way that companies claim credit for their methane emissions reductions is to use a carbon dioxide equivalent number. And what’s come into favor is this figure based on 20 years, which is what gets you methane is 80 times [as potent as carbon dioxide].
McKenzie: Could you explain a little bit more about where that comparison came from and why that is a flawed descriptor?
Pierrehumbert: The 80 times figure comes from the standard Global Warming Potential framework, which was introduced in the very first IPCC (Intergovernmental Panel on Climate Change) report, but what everybody forgot was that it was introduced as an example of how to do a comparison, and not as something people should actually use to make decisions. Nonetheless, it stuck.
The main thing is that there is no true equivalence between carbon dioxide emissions and methane emissions, because the climate responds in different ways to a short-lived gas than to a long-lived gas. If you put a kilogram of carbon dioxide in the atmosphere, it has a warming effect that lasts millennia. You put a kilogram of methane in the atmosphere, the warming effect will disappear almost entirely after 20 years.
So the amount of warming you get depends on the emission rate of methane, not the amount of emissions you put in the atmosphere. A kilogram per year gives you a certain amount of warming, because it doesn’t accumulate in the atmosphere beyond about 20 years. Whereas, a kilogram per year of carbon dioxide will mount up to a certain amount of warming in the first 20 years.
But if you keep emitting that kilogram per year, the amount of warming you get continues to increase indefinitely, which does not happen with methane. So any equivalence that says that a certain mass of methane is equivalent to this other mass of carbon dioxide, one megaton of methane is worth a certain number of megatons of carbon dioxide, anything like that is going to distort the climate response.
There is a way to compare them, which is to compare the actual amount of warming produced by different strategies... (MORE - missing details)
https://thebulletin.org/2023/12/mass-del...bly-wrong/
INTRO (excerpt): . . . The popular narrative suggests that tackling methane emissions is the “low-hanging fruit” in the climate-solutions toolbox. The belief that turning off the taps on this “super-pollutant” could “buy us time” to address the climate crisis is widespread, shared by politicians, journalists, and even some scientists.
But this is a dangerous fallacy, according to Raymond Pierrehumbert, a professor of physics at the University of Oxford and a member of the Bulletin of the Atomic Scientists Science and Security Board.
In an in-depth interview with Bulletin climate editor Jessica McKenzie, Pierrehumbert dissects the Oil and Gas Decarbonization Charter—the voluntary pledge made at COP28 by some oil and gas companies to slash operational emissions of greenhouse gases, including bringing methane emissions to “near-zero.”
He goes on to explain why describing methane as “80 times as potent as carbon dioxide” is inaccurate and misleading, and why the widespread hope that sharp cuts to methane emissions will bring about immediate and significant reductions of global temperatures is both wrong and distressing.
- - - INTERVIEW EXCERPT - - -
Raymond Pierrehumbert: . . . Now as far as methane goes—that’s where we get into the subtler issue of just what is carbon dioxide equivalent, or just all the fallacies associated with the term carbon dioxide equivalent, because the standard way that companies claim credit for their methane emissions reductions is to use a carbon dioxide equivalent number. And what’s come into favor is this figure based on 20 years, which is what gets you methane is 80 times [as potent as carbon dioxide].
McKenzie: Could you explain a little bit more about where that comparison came from and why that is a flawed descriptor?
Pierrehumbert: The 80 times figure comes from the standard Global Warming Potential framework, which was introduced in the very first IPCC (Intergovernmental Panel on Climate Change) report, but what everybody forgot was that it was introduced as an example of how to do a comparison, and not as something people should actually use to make decisions. Nonetheless, it stuck.
The main thing is that there is no true equivalence between carbon dioxide emissions and methane emissions, because the climate responds in different ways to a short-lived gas than to a long-lived gas. If you put a kilogram of carbon dioxide in the atmosphere, it has a warming effect that lasts millennia. You put a kilogram of methane in the atmosphere, the warming effect will disappear almost entirely after 20 years.
So the amount of warming you get depends on the emission rate of methane, not the amount of emissions you put in the atmosphere. A kilogram per year gives you a certain amount of warming, because it doesn’t accumulate in the atmosphere beyond about 20 years. Whereas, a kilogram per year of carbon dioxide will mount up to a certain amount of warming in the first 20 years.
But if you keep emitting that kilogram per year, the amount of warming you get continues to increase indefinitely, which does not happen with methane. So any equivalence that says that a certain mass of methane is equivalent to this other mass of carbon dioxide, one megaton of methane is worth a certain number of megatons of carbon dioxide, anything like that is going to distort the climate response.
There is a way to compare them, which is to compare the actual amount of warming produced by different strategies... (MORE - missing details)
